I am making an irish red this weekend and will be pitching Nottingham into it. I will let that ferment for 3 weeks and then I will brew by next beer and for the first time I will reuse the yeast cake. Usually when i brew, before I pitch yeast I aerate with a paint mixer paddle on my power drill. This really churns things up. Is there any issue doing this with an already existing yeast cake? Is aeration even necessary since a yeast cake should provide an abundance of strong active yeast for the fermentation? If I don’t churn things up with the paddle do I at least need to stir the beer to get the yeast into suspension or is it sufficient to just add the wort on top of the cake and allow nature to do it’s thang?
That’s a good question! The yeast need the oxygen for their reproductive phase, but if you have an entire yeast cake you’ll have a large enough colony for them to just start fermenting immediately. I would think you wouldn’t need to aerate in this case. I hope one of the yeast experts chimes in here, though, in case there are other benefits beyond reproduction.
I’ve always aerated when pitching on a yeast cake and haven’t had any bad results. I can’t say that not aerating is fine from direct experience, but it makes sense that it should work. No reason to churn it up just for the purposes of getting them suspended - the yeast will take care of that.
I do it all the time with my Mix-Stir and never had an issue with it.
I have done both. I probably need to aerate more than I do but here’s an example of a lager I’m brewing today just pumped through the chiller to the carboy. Seems pretty well aerated doesn’t it? Should I still hit it with the O2 stone?
You know, I guess when you think about it there is probably a fair amount of aeration that takes place if you just allow the wort to fall from the siphon tube and splash into the fermenting vessel. It likely does not need additional aeration.
[size=200]ˆ[/size] Definitely this.
I have always just let the wort splash in vigorously, or let it fan out over the inside wall of the fermentation vessel and it has always seemed to be quite effective and given me clean, healthy, vigorous, and sometimes quick fermentations.
If I were running a commercial operation I’d feel differently, but this definitely is one of those homebrewing categories where the process only needs to be a complicated as one wishes to make it…sometimes, the easy “cheap and dirty” way works just as well with a lot less fussing.
Ditto. One minute usually does the trick. 3-4 mins if it is a lager.
Start by thinking about the purpose of aeration. Yeast uses O2 to synthesize sterols which are used to keep cell walls flexible and promote budding, i.e. yeast growth. If you pitch on a slurry, there’s likely very little need for yeast growth. You have plenty to start with.
I mix with my impeller on a drill that I use. Sort of like a paint stirrer but more. My theory is that even if the aeration is not necessary it mixes the yeast into the wort and puts more yeast in direct contact with wort than leaving it sitting in the bottom.
I’m also in the boat of a vigorous pour out of my kettle on the yeast cake. So far this has netted a good fast start and fast ferment with no issues.
